Background: The objective of this study was to investigate the genetic fingerprints of class D oxacillinase positive imipenem-resistant Acinetobacter baumannii clinical isolates.Methods: Sixty clinical isolates of A. baumannii collected from Imam Hossein and Shahid Motahari Hospitals between October 2011 to April 2012 were employed. Presence of class D oxacillinases was shown by PCR and genotyping was performed using random amplified polymorphic DNA (RAPD-PCR). Correlation between class D gene carriage and RAPD-PCR patterns was studied among the isolates.Results: Majority of the imipenem-resistant isolates carried class D oxacillinase genes of which, 80% carried OXA-23, 60% had OXA-51, 61.66% harbored OXA-58 and 20% of the isolates carried OXA-24. It should be noted that in most isolates there was more than one gene. RAPD-PCR revealed three clusters (A-C) on a similarity level of 70% among which 53.3% belonged to cluster A, 41.7% were placed in cluster B and 5% in cluster C. On a similarity level of 85%, 10 groups were observed (1-10) of which, 28.3% were placed in pattern 1, 18.3 % had 8 pattern. OXA-23 was observed in 80 % of the isolates among which 29.2% belonged to pattern1; 20.8% were in pattern 8 and 16.6% of them were in pattern 9.Conclusion: OXA-23 was the most prevalent oxacillinase among our isolates. In addition, distribution of the majority of OXA-23 positive isolates in only 3 patterns suggests the clonal spread of these important pathogens.